Explosion suppression



E. D. REDDAN EXPLOSION SUPPRESSION Filed April 14. 1954' IN V E N TO REDWIN D. REDDAN ATTOR N E Y EXPLOSIUN SUPPRESSION Edwin D. Reddan,Wellesley, Mass., assignor to Electronics Corporation of America, acorporation of Mas sachusetts Application April 14, 1954, Serial No.423,194

2 Claims. (Cl. 169-28) This invention relates to extinguishing devicesof the type comprising a container for an extinguishing agent and adetonator arranged to burst the container and scatter the extinguishingagent in the presence of a fire or of an incipient explosion.

As compared with the explosion of a substance which carries its ownoxygen, an explosion of a mixture such as that of air and gasoline hasthe characteristic that the rate of development of pressure isrelatively slow; thus, for example, an explosion of a mixture of air andparaffin spray make take .2 to .3 second to develop a maximum pressureof about 40 to 60 pounds per square inch; and gasoline vapor in free airdevelops a pressure of about 80 pounds per square inch approximately .04second after ignition.

Thus an explosion of a mixture of a combustible vapor with air beginswith a relatively slow build-up of energy, with correspondingly slowrises of pressure, heat, and radiation. This rise may be spread overseveral hundredths of a second before a critical energy level is reachedand a dangerous explosive pressure is developed.

An explosion detector and suppressor system has been proposed in whichthe detector comprises a pressureresponsive diaphragm which detects therise in pressure occurring in an incipient explosion. This detector isconnected in an electric circuit including a contact adapted to beclosed by the detector to release an extinguishing agent. The detectoris made to respond to a small pressure rise when the rate of pressurerise is in excess of 50 pounds per square inch per second, and iscapable of closing the contact within .02 second of the initiation ofthe pressure rise. The suppressor is capable of distributing theextinguishing agent within .05 second of the initiation of the pressurerise. The suppressor comprises a frangible container for theextinguishing agent. A rapidly-acting detonator, which acts in responseto the closing of the detector contact, is arranged to burst thecontainer and thus scatter the extinguishing agent which it contains.This system is described in detail in British Patent No. 643,189,published September 15, 1950.

Another explosion detector has been proposed which is responsive to therate of rise of electromagnetic radiation which occurs in an incipientexplosion. This explosion detector comprises a photocell the output ofwhich is connected to an electronic valve through a differentiatingnetwork. This valve, which is normally nonconductive, conducts when thephotocell detects a sharp rise of radiation of the type found inincipient explosions. Conduction through the valve actuates theexplosion suppressor. This explosion detector of the radiation type isdescribed in United States Patent Application Serial No. 364,142, filedJune 25, 1953, by Bradford T. Joyce and Alfred F. Krueger, and entitledExplosion Detection and Suppression.

A typical application of these explosion detector and suppressor systemslies in the protection of fuel tanks, particularly those of militaryaircraft which may be penetrated by incendiary bullets. When thisoccurs, the fuel 2,760,586 Patented Aug. 28, 1956 vapor in the tanks isignited and explodes, fracturing part of the aircraft structure or wingand scattering burning fuel over it, causing the aircraft to come downin flames.

In suppressors designed to protect the fuel tanks of aircraft, thecontainer for the extinguishing agent must be made of a material whichis not attacked by the fuel or by the extinguishing agent. Also, whenthe suppressor is operated, it must not burst into fragments of suchsmall size that they might clog the fuel system of the aircraft.

One suitable suppressor comprises a relatively stifi backing plate whichincludes a housing for a detonator. A frangible, phenolic-impregnatedfabric hemisphere is securely attached to the backing plate, forming asealed cavity in which the extinguishing agent is placed. When thedetonator is blown, the hemisphere breaks into relatively large pieces,and the extinguishing agent is scattered throughout the protected tankas a fine mist. While this type of suppressor is sufliciently tough notto be shattered by exploding another suppressor of the same type in itsvicinity, it has, in some instances, been shattered by fragments ofincendiary bullets before an explosion detector of the pressure-risetype could detect the incipient explosion. Such a premature shatteringof the suppressor resulted in failure to suppress the explosion, as theproper distribution of the extinguishing agent through the tank can onlybe obtained by shattering the suppressor by means of the detonator.

It is the principal object of this invention to provide an explosionsuppressor which does not shatter prematurely when hit externally byflying fragments, which ruptures when the pressure inside the suppressoris increased by the firing of the detonator and thus scatters theextinguishing agent which it contains, and which does not rupture intopieces small enough to clog an aircraft fuel system.

In accordance with the illustrated embodiment of the present invention,the container for the extinguishing agent is made of a material theflexibility of which is such that the container may be visibly deformedwhen pressure is applied to it by hand, the container resuming itsnormal shape when the pressure is removed.

Referring to Figure 1, the explosion suppressor comprises a container 3for the extinguishing agent 5. This container 3 is made of a highlyflexible material such as the polymonochlorotrifluoroethylene plasticsold by the M. W. Kellogg Company under the trademark of KEL-F. Thecontainer 3 is provided with a threaded neck portion 7. After thecontainer is filled with the extinguishing agent 5, it is sealed bymeans of a hollow plastic stopper 9 which fits inside and over the neckportion 7 of the container 3 and is heat-sealed thereto. The hollowstopper 9 is longer than the neck portion 7 of the container 3. Adetonator 11 is positioned in the stopper 9, the explosive charge of thedetonator being preferably located toward the bottom of stopper 9. Theneck portion 7 of the container 3 is screwed into the metal socket 113.The detonator 9 is provided with a shoulder portion 15 and with two malecontacts 17 which fit into two female contacts 19. Female contacts 19are electrically connected by means of wires 20 to outside terminals 21.For mounting purposes, the socket 13 is provided with a flange 23 whichmay be secured by means of rivets passed through holes 25 to the wall ofan aircraft fuel tank.

When a fire or explosion detector fires the detonator, the container 3bursts and scatters the extinguishing agent 5 which it contains. Thehighly flexible container 3 does not shatter when hit externally byfragments of an incendiary bullet; at worst it may puncture, in whichcase by the time the explosion caused by the incendiary bullet isdetected and the detonator is fired a sufiicient amount of extinguishingagent is still left in the container 3 to suppress the explosion.

I claim:

1. An explosion suppressor comprising: a sealed eontainer made of ahighly flexible material, an extinguish ing agent within said container,and a detonator having an explosive charge positioned within saidcontainer.

2. An explosion suppressor comprising: a container made of a highlyflexible material and having a threaded neck portion, a hollow stopperlonger than said neck portion and sealed thereto, an extinguishing agentpositioned within said container, and a detonator having an explosivecharge positioned within said hollow stopper.

References Cited in the file of this patent UNITED STATES PATENTSDelbare Apr. 24,

Buddecke Apr. 9,

Thompson Oct. 5,

FOREIGN PATENTS Great Britain Sept. 15,

1. AN EXPLOSION SUPPRESSOR COMPRISING: A SEALED CONTAINER MADE OF AHIGHLY FLEXIBLE MATERIAL, AN EXTINGUISHING AGENT WITHIN SAID CONTAINER,AND A DETONATOR HAVING AN EXPLOSIVE CHARGE POSITIONED WITHIN SAIDCONTAINER.